1. Field of the Invention
The present invention relates to a substrate processing method and a substrate processing apparatus for processing substrates. Examples of substrates to be processed include substrates such as semiconductor wafers, substrates for liquid crystal displays, substrates for FPDs (Flat Panel Displays) such as organic ELs (Electroluminescence), substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks, substrates for photomasks, ceramic substrates, substrates for solar cells, etc.
2. Description of the Related Art
In substrate processing by a single substrate processing type substrate processing apparatus, substrates are processed one at a time. In detail, a substrate is held substantially horizontally by a spin chuck. Then, after processing of an upper surface of the substrate by a chemical liquid, the upper surface of the substrate is rinsed by a rinse liquid. Thereafter, a spin drying step is executed in which the substrate is rotated at a high speed for drying the upper surface of the substrate.
As shown in FIG. 9, where a fine pattern is formed on a front surface of a substrate, in the spin drying step, it may not be possible to satisfactorily dry a rinse liquid which has entered into an interior of the pattern. Drying failure may occur thereby. A liquid surface (interface between air and liquid) of the rinse liquid that entered into an interior of the pattern is formed inside the pattern. Therefore, a surface tension of the liquid acts on a position at which the liquid surface is in contact with the pattern. Where the surface tension is large, the pattern may easily collapse. Since water that is a typical example of the rinse liquid is large in surface tension, collapse of a pattern cannot be ignored in the spin drying step.
Thus, there has been proposed a method for using isopropyl alcohol (IPA) which is a low surface-tension liquid lower in surface tension than water (refer to, for example, Japanese Patent Application Publication No. 2016-21597). Specifically, IPA is supplied to an upper surface of a substrate to replace water entered into an interior of a pattern by IPA and remove IPA thereafter, thereby drying the upper surface of the substrate. However, even where water that entered into the interior of the pattern is replaced by IPA, collapse of the pattern may occur, if a surface tension acts thereon for a longer time or the pattern is low in strength.
Thus, Japanese Patent Application Publication No. 2012-222329 has disclosed substrate processing by which an upper surface of a substrate is hydrophobized by a silylating agent to lower a surface tension applied to a pattern, thereby preventing collapse of the pattern. Specifically, a silylating agent is supplied to an upper surface of a substrate and the silylating agent supplied to the upper surface of the substrate flows so as to spread from a center of the upper surface of the substrate to a peripheral edge thereof due to rotation of the substrate. Thereby, the upper surface of substrate in its entirety is hydrophobized. Thereafter, the silylating agent that remains on the upper surface of the substrate is washed away by IPA and the substrate is then dried. The silylating agent and IPA which have been removed from the upper surface of the substrate are received by a cup portion.